measurement of t-violating transverse muon polarization in k + → p 0 m + n decay at ...
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Measurement of T-violating transverse muon polarization
in K+→ decay at J-PARC
Suguru SHIMIZU
Osaka University
for the E06(TREK) collaboration
June 5, 2007INPC’07, Tokyo
RE collaboration
Japan:– Osaka University– National Defense Academy (NDA)– Tohoku University– KEK
Canada:– University of Saskatchewan – University of British Columbia (UBC)– University of Montreal– TRIUMF
US:– MIT– University of South Carolina (USC)– Iowa State University (ISU)
Russia:– Institute for Nuclear Research (INR, Russia)
Vietnam:– University of Natural Sciences (UNS, Vietnam)
T K
Transverse muon polarization
Non-zero PT is a signature of T violation.
Standard model contribution is very small(10-7). Spurious effect from final state interaction is also small(10-5). Therefore, PT is sensitive to physics beyond the Standard Model.
Experiment at KEK(E246) PT = 0.0017 ± 0.0023(stat) ± 0.0011(syst) ( |PT | < 0.0050 : 90% C.L. ) PRD73, 72005(2006)
K+→decay
T-odd
Model descriptions of PT Multi-Higgs doublet (3 Higgs doublet) model (MH)
– Im = (mK2/mH
2) Im(11*)
– | Im(11*) | < 544 (mH/GeV)2 from the E246 limit
– B→X constraints also Im(11*) but weaker ( <1900 (mH/GeV)2 )
– N-EDM and b→s constraint differently Im(11*)
SUSY with s-quark mixing (SUS)– Im ∝ Im[V33
H+ V32DL* V31
UR*]/ mH2
– mH ≥ 140 GeV from the E246 limit and no stringent limit from other modes
SUSY with R-parity violation (SUR)– Iml ~ Im [2i2(i12)*], Imd ~ Im [’21k(’22k)*]– No stringent limits from other modes
• Stopped K+ method• Toroidal Spectrometer and CsI(Tl) calorimeter• Measurement of e+ asymmetry in cw/ccw direction
side view end view
decay
KEK-PS E246 experiment
PT = 0.0017 ± 0.0023(stat) ± 0.0011(syst)Im= 0.0053 ± 0.0071(stat) ± 0.0036(syst)
New experiment at J-PARC (TREK) We aim at a sensitivity of PT ~10-4 (E246-PT ~10-3) Reasonable upgrading of the E246 system
Statistical errorPT
stat ≤ 0.1 PTstat (E246) ~10-4 with
1) × 30 of beam intensity → rate capability of detectors
2) × 10 of detector acceptance
Systematic errorPT
syst ~ 0.1 PTsyst (E246) ~10-4 by
1) precise calibration of misalignments using data 2) correction of systematic effectsJPARC
J-PARC FacilityJ-PARC is now constructed at Tokai, Ibaraki.
Upgrade of the E246 detector for TREK at J-PARC
Muon polarimeter passive → active
Muon magnetic field toroid → muon field magnet
Target smaller and finer segmentation MPPC readout
Charged particle tracking addition of GEM around target
CsI(Tl) readout PIN → APD with current
amplifier
Active polarimeter Identification of muon stopping point/ decay vertex Measurement of positron energy Ee+ and angle e+ Large positron acceptance of nearly 4 Larger analyzing power Lower BG in positron spectraParallel plate stopper with Ga
p MWPC Number of plates 31 Plate material Al, Mg or alloy Plate thickness ~ 2 mm Plate gap ~ 8 mm Ave. density 0.24 Al
stop efficiency ~ 95%
Small systematics for L/R positron
Sensitivity estimate of TREK
Source PT • Net run time 1.0 ×107 s
-- one year run
• Proton beam intensity 9A on T1• K+ beam intensity 3×106 /s
-- 30 times of E246• Total number of good K3 2.4×109
-- detector acceptance: 8 times of E246• Total number of fwd/bwd (N) 7.2×108
• Sensitivity coefficient 3.73√N-- Analyzing power: 1.5 times of E246
Total ~ 10-4
Statistical sensitivity Systematic errors
Source PT
field alignment < 10-4
kinematic distortion < 10-4
polarimeter analysis < 10-
4
Total <10-4
JPARC
Summary
We aim at a sensitivity of PT ~10-4 for statistical and systematic errors.
New K+ beam line (K0.8). Reasonable upgrading of the E246 system,
(1)active polarimeter, (2)readout of calorimeter, (3)tracking system.
Systematic errors have been carefully checked by MC.New detector components have been tested.Next step is stage-2 approval (stage-1 was already appro
ved).
• backup
Beamline for K+ extraction
Momentum 800 MeV/cMomentum bite ±2.5%Acceptance 6.5 msr % p/pK+ intensity 3 ×106 /sK/ ratio > 2Beam spot 1.04 ×0.78 cm (FWQM)Final focus achromatic
K0.8 ( K1.1-BR)
proton
Final Focus
Single stage DC separator
Vertical focuses before and after the separator
Horizontal focus just afterthe second D-magnet
E246 result
PT = 0.0017 ± 0.0023(stat) ± 0.0011(syst) ( |PT | < 0.0050 : 90% C.L. )
Im= 0.0053 ± 0.0071(stat) ± 0.0036(syst)
( |Im| <0.016 : 90% C.L. )Statistical error dominant
AT = (Afwd - Abwd ) / 2
Ncw - NccwAfwd(bwd) = Ncw + Nccw
PT = AT / {<cosT>} : analyzing power <cosT> : attenuation factor Im = PT / KF
KF : kinematic factor
PRD73, 072005(2006)
Status of TREK
• Stage-1 approval in the first PAC meeting in June-July, 2006.
• Now;– Studies of detector upgrade– Polarimeter alignment procedure– Muon field magnet
• Seek for funding• Grouping Most important issues〉
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